Aluminum alloy fin material for heat exchanger, method for manufacturing same, heat exchanger using said aluminum alloy fin material and method for manufacturing same

ABSTRACT

There are provided: an aluminum alloy fin material for a heat exchanger, the aluminum alloy fin material including an aluminum alloy including 0.70 to 1.50 mass % Si, 0.05 to 2.00 mass % Fe, 1.0 to 2.0 mass % Mn, 0.5 to 4.0 mass % Zn, with a balance consisting of Al and inevitable impurities, in which before brazing heating, the amount of solid solution Si is 0.60 mass % or less, and the amount of solid solution Mn is 0.60 mass % or less, and in which a recrystallization temperature in a temperature rise process during the brazing heating is 450° C. or less; a method of producing the aluminum alloy fin material; a heat exchanger using the aluminum alloy fin material; and a method of producing the heat exchanger.

TECHNICAL FIELD

The present disclosure relates to: an aluminum alloy fin material for aheat exchanger, specifically an aluminum alloy fin material for a heatexchanger in which fin and a component material of a working fluidpassage are joined to each other by brazing, such as a radiator, aheater core, an oil cooler, an intercooler, a condenser, or anevaporator in a car air conditioner, particularly an aluminum alloy finmaterial for a heat exchanger having excellent resistance to melting ofa fin during brazing and excellent high-temperature durability after thebrazing; a method of producing the aluminum alloy fin material; a heatexchanger to which the aluminum alloy fin material is assembled; and amethod of producing the heat exchanger.

BACKGROUND ART

Aluminum alloys are lightweight and have high thermal conductivity, andthe high corrosion resistance of such aluminum alloys can be achieved byappropriate treatment. Therefore, such aluminum alloys have been used inheat exchangers for use in automobiles and the like, such as radiators,condensers, evaporators, heaters, intercoolers, and oil coolers. Atwo-layered tube material in which an Al—Mn-based alloy such as a 3003alloy is used as a core material and one surface of the core material iscladded with a brazing filler material with an Al—Si-based alloy or asacrificial anode material with an Al—Zn-based alloy, a three-layeredtube material in which the other surface is further cladded with abrazing filler material with an Al—Si-based alloy, or the like is usedas a tube material for an automotive heat exchanger. Heat exchangers aretypically joined by combining such tube materials and corrugatedaluminum alloy fin materials and brazing the tube materials and thecorrugated aluminum alloy fin materials at a high temperature of around600° C.

In such heat exchangers, pure aluminum-based alloys such as JIS 1050alloys excellent in thermal conductivity and Al—Mn-based alloys such asJIS 3003 alloys excellent in strength and buckling resistance have beencommonly used as aluminum alloy fin materials.

In recent years, the reduced weights, reduced sizes, and enhancedperformance of heat exchangers have been increasingly demanded. As aresult, it has been particularly demanded that aluminum alloy finmaterials to be joined by brazing have thin thicknesses, favorablebrazability, and moreover excellent characteristics such as strength,thermal conductivity, and corrosion resistance after brazing heating.However, such thinner thicknesses have particularly precluded thesolution of such problems as described below.

There is a problem in that a fin is corroded by a brazing-fillergenerated from an Al—Si-based brazing filler material during brazing,whereby the fin is melted at the grain boundary. Because Zn and Si aresegregated at the grain boundary, the concentrations of Zn and Si at thegrain boundary are higher than those in a matrix, and the grain boundaryis in a state in which a melting point is lower. Moreover, Si diffusesfrom the melted brazing-filler into the fin during the brazing. In sucha case, the diffusion rate of Si at the grain boundary is much higherthan the diffusion rate of Si in the matrix, and therefore, a largeamount of Si diffuses particularly into a grain boundary. Because Sidiffuses into the overall sheet thickness of the fin, the influence ofthe diffusion is not large when the sheet thickness of the fin is large.However, when the sheet thickness is small, the amount of Si solidsolution in the grain boundary of a fin material greatly increases, themelting point of the grain boundary decreases, and the fin is melted.Therefore, it is necessary to, in advance, reduce the amount of Si solidsolution in the fin material before the brazing.

A technology for reducing the amount of solid solution Si in a finmaterial is described in Patent Literature 1. In the technology, theintergranular corrosion of a fin is assumed to be able to be suppressedby setting the amount of Si solid solution at 0.7% or less in the centerof a fin thickness after brazing heating. However, the technology is notassumed to be intended to solve the problem of melting of a fin in agrain boundary. Therefore, the problem in that resistance to melting ofa fin is influenced not only by the amount of solid solution Si beforebrazing but also by segregation at a grain boundary is not recognized atall, and a method of solving the problem is not suggested at all.

There is another problem in that durability is poor at high temperature.For example, in the case of use as a fin for a radiator, cooling waterflowing into a tube has a high temperature of around 85 to 120° C., thetube is repeatedly bulge due to internal pressure, and high-temperaturefatigue damage to the fin is caused. Therefore, rupture is caused by thehigh-temperature fatigue damage when the sheet thickness of the fin issmall.

A technology for improving the durability of a fin is described inPatent Literature 2. In the technology, control of an Al—(Mn,Fe)—Si-based compound to an appropriate number density is assumed toallow the strength of a fin material after brazing heating to beimproved, thereby improving strength as a heat exchanger, that is,durability. In the technology, however, the heat exchanger having a hightemperature is not mentioned at all, and therefore, a method of solvingthe problem of a rupture of the fin due to high-temperature fatiguedamage is not suggested at all.

CITATION LIST Patent Literature

Patent Literature 1: Unexamined Japanese Patent Application KokaiPublication No. 2004-084060

Patent Literature 2: Unexamined Japanese Patent Application KokaiPublication No. 2012-126950

SUMMARY OF INVENTION Technical Problem

As described above, it has been difficult in conventional technologiesto provide an aluminum alloy fin material that suppresses melting of afin in a grain boundary during brazing in the case of using an aluminumalloy fin material thin in thickness in a heat exchanger and thatmoreover has excellent high-temperature durability after the brazing.

The present disclosure was accomplished in order to solve theabove-described problems, with an objective of providing: an aluminumalloy fin material for a heat exchanger, having excellent resistance tomelting of a fin during brazing and having excellent high-temperaturedurability after the brazing; a method of producing the aluminum alloyfin material; a heat exchanger for use in an automobile and/or the like,using the aluminum alloy fin material; and a method of producing theheat exchanger.

Solution to Problem

In claim 1, the present disclosure provides an aluminum alloy finmaterial for a heat exchanger, the aluminum alloy fin material includingan aluminum alloy including 0.70 to 1.50 mass % Si, 0.05 to 2.00 mass %Fe, 1.0 to 2.0 mass % Mn, 0.5 to 4.0 mass % Zn, with a balanceconsisting of Al and inevitable impurities, wherein before brazingheating, the amount of solid solution Si is 0.60 mass % or less, and theamount of solid solution Mn is 0.60 mass % or less, and wherein arecrystallization temperature in a temperature rise process during thebrazing heating is 450° C. or less.

In claim 2, the present disclosure provides the aluminum alloy finmaterial for a heat exchanger according to claim 1, wherein in thealuminum alloy after brazing heating, the amount of solid solution Mn is0.60 mass % or less, and each of values of S1/S2 and Z1/Z2 is 1.20 orless when the concentrations of Si and Zn in the vicinity of a grainboundary are assumed to be S1 mass % and Z1 mass %, respectively, andthe concentrations of Si and Zn in a matrix are assumed to be S2 mass %and Z2 mass %, respectively.

In claim 3, the present disclosure provides the aluminum alloy finmaterial for a heat exchanger according to claim 1 or 2, wherein thealuminum alloy further includes one or more selected from 0.05 to 0.30mass % Cu, 0.05 to 0.30 mass % Ti, 0.05 to 0.30 mass % Zr, 0.05 to 0.30mass % Cr, and 0.05 to 0.30 mass % V.

In claim 4, a method of producing an aluminum alloy fin material for aheat exchanger of the present disclosure, according to Embodiment 1, isa method of producing the aluminum alloy fin material for a heatexchanger according to any one of claims 1 to 3, the method including astep of casting the aluminum alloy, a hot-rolling step of hot-rolling acast ingot, a cold-rolling step of cold-rolling a hot-rolled sheet, andone or more annealing steps of annealing a cold-rolled sheet in or afterthe cold-rolling step, or in and after the cold-rolling step, whereinthe hot-rolling step includes a heating stage, a retention stage, and ahot-rolling stage, wherein in the heating stage, a heating rate fromattainment of 400° C. to attainment of a retention temperature in theretention stage is 60° C./h or less, wherein in the retention stage, theretention temperature is 450 to 560° C., and a retention time is 0.5hour or more, wherein in the hot-rolling stage, a time for which thehot-rolled sheet has a temperature of 400° C. or more is 5 minutes ormore, and wherein in the cold-rolling step, the cold-rolled sheet has atemperature of 120° C. or less.

In claim 5, a method of producing an aluminum alloy fin material for aheat exchanger of the present disclosure, according to Embodiment 2, isa method of producing the aluminum alloy fin material for a heatexchanger according to any one of claims 1 to 3, the method including astep of casting the aluminum alloy, a homogenization treatment step ofhomogenization-treating a cast ingot, a hot-rolling step of hot-rollinga homogenization-treated ingot, a cold-rolling step of cold-rolling ahot-rolled sheet, and one or more annealing steps of annealing acold-rolled sheet in or after the cold-rolling step, or in and after thecold-rolling step, wherein the homogenization treatment step includes aheating stage, a retention stage, and a cooling stage, wherein in theheating stage, a heating rate from attainment of 400° C. to attainmentof a retention temperature in the retention stage is 60° C./h or less,wherein in the retention stage, the retention temperature is 450 to 560°C., and a retention time is 1.0 hour or more, wherein in the coolingstage, a cooling rate before the ingot attains a temperature of 400° C.is 60° C./h or less, and wherein in the cold-rolling step, thecold-rolled sheet has a temperature of 120° C. or less.

In claim 6, the present disclosure provides a heat exchanger to whichthe aluminum alloy fin material according to any one of claims 1 to 3 isassembled by brazing.

In claim 7, the present disclosure provides a method of producing theheat exchanger according to claim 6, the method including subjecting acombination of the aluminum alloy fin material according to any one ofclaims 1 to 3 with another member to brazing heating at an attainmenttemperature of 590 to 615° C. for 2 to 6 minutes, wherein arecrystallization temperature in a temperature rise process duringbrazing is set at 450° C. or less, and a heating rate in a temperaturerange of 300 to 580° C. is set at 60 to 160° C./min.

Advantageous Effects of Invention

According to the present disclosure, there are provided: an aluminumalloy fin material for a heat exchanger, having excellent resistance tomelting of a fin during brazing and exhibiting excellenthigh-temperature durability after the brazing; and a heat exchanger foruse in an automobile and/or the like, using the aluminum alloy finmaterial. The aluminum alloy fin material according to the presentdisclosure is preferably used as a fin material for a heat exchanger foruse in an automobile and/or the like because of having not onlyexcellent formability but also excellent corrosion resistance andexcellent thermal conductivity after brazing heating.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of an aluminum alloy fin material according to thepresent disclosure, a method of producing the aluminum alloy finmaterial, and a heat exchanger using the aluminum alloy fin materialwill be described in detail.

1. Constitution of Aluminum Alloy Fin Material, and Method of SupplyingBrazing-Filler

The aluminum alloy fin material for a heat exchanger according to thepresent disclosure (hereinafter simply referred to as “aluminum alloyfin material”) is assumed to be a bare material with a one-layerconstitution, which is not cladded with a skin material such as abrazing filler material. A brazing-filler needed for brazing is suppliedby, for example, cladding of a low-melting-point Al—Si alloy on a flowpassage formation component which becomes an opposite material forjoining.

2. Alloy Compositions

In the aluminum alloy fin material according to the present disclosure,an aluminum alloy including 0.70 to 1.50 mass % (hereinafter simplyreferred to as “%”) Si, 0.05 to 2.00% Fe, 1.0 to 2.0% Mn, and 0.5 to4.0% Zn as essential elements, with a balance consisting of Al andinevitable impurities. The aluminum alloy may also further include, asselective additional elements, one or more selected from 0.05 to 0.30%Cu, 0.05 to 0.30% Ti, 0.05 to 0.30% Zr, 0.05 to 0.30% Cr, and 0.05 to0.30% V. In addition to the essential elements and the selectiveadditional elements, 0.15% in total of Ni, Co, and the like, of whicheach is 0.05% or less, may be further contained as inevitableimpurities. Each composition will be described in detail below.

Si

Si forms, together with Fe and Mn, Al—Fe—Si-based, Al—Mn—Si-based, andAl—Fe—Mn—Si-based intermetallic compounds, improves strength due todispersion strengthening, or forms a solid solution in an aluminummatrix, thereby improving strength due to solid solution strengthening.The content of Si is 0.70 to 1.50%. A Si content of less than 0.70%causes the above-described effects to be insufficient, while a Sicontent of more than 1.50% results in a decrease in a melting point,whereby melting is more likely to occur. The preferred content of Si is0.75 to 1.20%.

Fe

Fe forms, together with Si and Mn, an Al—Fe—Mn—Si-based intermetalliccompound, and improves strength due to dispersion strengthening. Thecontent of Fe is 0.05 to 2.00%. An Fe content of less than 0.05%requires use of a high-purity aluminum base metal, thereby resulting inan increased cost. In contrast, an Fe content of more than 2.00% isprone to result in formation of a giant intermetallic compound incasting, thereby deteriorating plastic workability. The preferredcontent of Fe is 0.10 to 1.50%.

Mn

Mn forms, together with Si, an Al—Mn—Si-based intermetallic compound,forms, together with Si and Fe, an Al—Mn—Fe—Si-based intermetalliccompound, improves strength due to dispersion strengthening, or forms asolid solution in an aluminum matrix, thereby improving strength due tosolid solution strengthening. The content of Mn is 1.0 to 2.0%. A Mncontent of less than 1.0% causes the above-described effects to beinsufficient, while a Mn content of more than 2.0% is prone to result information of a giant intermetallic compound in casting, therebydeteriorating plastic workability. The preferred content of Mn is 1.1 to1.8%.

Zn

Zn can result in a lower pitting potential, and can result in formationof a potential difference from a brazed opposite material such as atube, thereby improving the corrosion resistance of the oppositematerial due to a sacrificial protection effect. The content of Zn is0.5 to 4.0%. A Zn content of less than 0.5% causes the effect ofimproving corrosion resistance due to the sacrificial protection effectto be insufficiently obtained. In contrast, a Zn content of more than4.0% results in the increased corrosion rate of a fin, causes the fin todisappear early, and results in insufficient corrosion resistance. Thepreferred content of Zn is 1.0 to 3.5%.

Cu

Cu may be contained because of improving strength due to solid solutionstrengthening. The content of Cu is 0.05 to 0.30%. A Cu content of lessthan 0.05% causes the above-described effect to be insufficient, while aCu content of more than 0.30% results in a higher pitting potential andresults in an insufficient sacrificial protection effect. The preferredcontent of Cu is 0.10 to 0.30%.

Ti

Ti may be contained because of improving strength due to solid solutionstrengthening. The content of Ti is 0.05 to 0.30%. A Ti content of lessthan 0.05% causes the above-described effect to be insufficient. A Ticontent of more than 0.30% is prone to result in formation of a giantintermetallic compound, thereby deteriorating plastic workability. Thepreferred content of Ti is 0.10 to 0.20%.

Zr

Zr may be contained because of improving strength due to solid solutionstrengthening and having the effect of causing precipitation of anAl—Zr-based intermetallic compound, thereby coarsening crystal grainsafter brazing heating. The content of Zr is 0.05 to 0.30%. A Zr contentof less than 0.05% prevents the above-described effects from beingobtained. A Zr content of more than 0.30% is prone to result information of a giant intermetallic compound, thereby deterioratingplastic workability. The preferred content of Zr is 0.10 to 0.20%.

Cr

Cr may be contained because of improving strength due to solid solutionstrengthening and having the effect of causing precipitation of an Al—Cr-based intermetallic compound, thereby coarsening crystal grains afterbrazing heating. The content of Cr is 0.05 to 0.30%. A Cr content ofless than 0.05% prevents the above-described effects from beingobtained. A Cr content of more than 0.30% is prone to result information of a giant intermetallic compound, thereby deterioratingplastic workability. The preferred content of Cr is 0.10 to 0.20%.

V

V may be contained because of not only improving strength due to solidsolution strengthening but also improving corrosion resistance. Thecontent of V is 0.05 to 0.30%. A V content of less than 0.05% preventsthe above-described effects from being obtained. A V content of morethan 0.30% is prone to result in formation of a giant intermetalliccompound, thereby deteriorating plastic workability. The preferredcontent of V is 0.10 to 0.20%.

At least one of such Cu, Ti, Zr, Cr, and V may be optionally added.

3. Amount of Solid Solution Before and After Brazing

In the aluminum alloy fin material according to the present disclosure,the amounts of solid solution Si and solid solution Mn before brazingheating are limited to 0.60% or less and 0.60% or less, respectively.Such limitations are intended to prevent a fin from being melted duringbrazing heating and to improve high-temperature durability after thebrazing heating. The reasons of the limitations will be described below.

As already mentioned, a large amount of Si diffuses from a meltedbrazing-filler along the grain boundary of a fin material duringbrazing, thereby resulting in a decrease in a melting point at the grainboundary of the fin material. Because it is impossible to prevent suchdiffusion of Si during brazing, it is important to, in advance, reducethe amount of solid solution Si in the fin material before the brazing.When the amount of solid solution Si before the brazing is 0.60% orless, the total concentration of Si at the grain boundary can be reducedto not more than a predetermined level even if a large amount of Sidiffuses from the melted brazing-filler along the grain boundary of thefin material, and therefore, a decrease in melting point at the grainboundary during the brazing can be suppressed to prevent the grainboundary from being melted. When the amount of solid solution Si beforethe brazing is more than 0.60%, the diffusion of a large quantity of Sifrom the melted brazing-filler along the grain boundary of the finmaterial allows the total concentration of Si at the grain boundary tobe more than the predetermined level, and therefore, the melting pointof the grain boundary during the brazing decreases, thereby resulting inthe melting of the grain boundary. Therefore, the amount of solidsolution Si before the brazing is regulated to 0.60% or less, andpreferably to 0.55% or less. The lower limit value of the amount ofsolid solution Si before the brazing is not limited from the viewpointof melting during brazing, but it is difficult to set the lower limitvalue at 0.05% or less within the range of a Si content set in thepresent disclosure.

As already mentioned, for example, in the case of use as a fin for aradiator, cooling water flowing into a tube has a high temperature ofaround 85 to 120° C., the tube is repeatedly bulge due to internalpressure, and high-temperature fatigue damage to the fin is caused.However, a phenomenon in which part of the caused fatigue damage isrecovered at high temperature is seen. As a result of repeatedlyconducting intensive research, the present inventors revealed that solidsolution Mn is a factor that prevents such a recovery. On the basis ofthe fact, the present inventors found that high-temperature durabilitycan be improved by reducing the amount of solid solution Mn afterbrazing heating to a low level.

Specifically, when the amount of solid solution Mn after brazing heatingis 0.60% or less, the fatigue damage is sufficiently recovered, andexcellent high-temperature durability can be obtained. When the amountof solid solution Mn after brazing is more than 0.60%, the recovery ofthe fatigue damage is prevented, and high-temperature durability becomesinsufficient. Therefore, the amount of solid solution Mn after brazingis regulated to 0.60% or less, and preferably to 0.55% or less.

Because the solid solutions of Al—Mn—Si-based, Al—Fe—Mn—Si-based, andAl—Mn-based intermetallic compounds are generated in brazing, the amountof solid solution Mn after brazing is more than that before brazing.Therefore, it is impossible to set the amount of solid solution Mn in astate after brazing at 0.60% or less unless at least a condition thatthe amount of solid solution Mn in a state before brazing is 0.60% orless is satisfied. Therefore, the amount of solid solution Mn beforebrazing is also regulated to 0.60% or less. As a result, excellenthigh-temperature durability is exhibited. In contrast, when the amountof solid solution Mn before brazing is more than 0.60%, it is impossibleto reduce the amount of solid solution Mn after brazing to 0.60% orless, and it is impossible to obtain excellent high-temperaturedurability. On the basis of the above, the amounts of solid solution Mnbefore and after brazing are regulated to 0.60% or less, and preferablyto 0.55% or less. The lower limit values of the amounts of solidsolution Mn before and after brazing are not limited from the viewpointof high-temperature durability, but it is difficult to set the lowerlimit values at 0.05% or less within the range of a Mn content set inthe present disclosure.

4. Grain Boundary Segregation after Brazing

In the aluminum alloy fin material according to the present disclosure,each of the values of S1/S2 and Z1/Z2 is set at 1.20 or less when theconcentrations of Si and Zn in the vicinity of a grain boundary areassumed to be S1% and Z1%, respectively, and the concentrations of Siand Zn in a matrix are assumed to be S2% and Z2%, respectively, duringbrazing. Such limitations are intended to prevent a fin from beingmelted during brazing. The reasons of the limitations will be describedbelow.

Recrystallization occurs in an aluminum alloy fin material duringbrazing. As already mentioned, because Zn and Si are segregated at thegrain boundary, the concentrations of Zn and Si in the vicinity of thegrain boundary are higher than those in a matrix, and the grain boundaryis in a state in which a melting point is lower. Therefore, suppressionof grain boundary segregation during brazing is required for suppressingmelting of a fin.

As a result of repeatedly conducting intensive research, the presentinventors found that melting of a grain boundary can be suppressed in acase in which each of a ratio between the amounts of solid solution Znand a ratio between the amounts of solid solution Si in the vicinity ofa grain boundary and in a matrix after brazing, that is, each of thevalues of S1/S2 and Z1/Z2 is 1.20 or less when the concentrations of Siand Zn in the vicinity of the grain boundary are assumed to be S1% andZ1%, respectively, and the concentrations of Si and Zn in the matrix areassumed to be S2% and Z2%, respectively. When each of the values ofS1/S2 and Z1/Z2 is 1.20 or less, grain boundary segregation duringbrazing is sufficiently suppressed, and a grain boundary is not melted.When one or both of the values of S1/S2 and Z1/Z2 are more than 1.20,suppression of grain boundary segregation during brazing isinsufficient, and a grain boundary is melted. Both the preferred valuesof S1/S2 and Z1/Z2 are 1.10 or less. The lower limit values of S1/S2 andZ1/Z2 are not limited from the viewpoint of melting of a fin, but whenthe amount of solid solution element in the vicinity of a grain boundaryis much smaller than that in a matrix, the element in the matrixdiffuses into the grain boundary, and therefore, it is difficult to seteach of S1/S2 and Z1/Z2 at 0.50 or less.

In a cooling process in brazing, precipitation preferentially occurs inthe vicinity of a grain boundary, and the amount of solid solution inthe vicinity of the grain boundary is reduced. Therefore, even if grainboundary segregation occurs during brazing, the amount of solid solutionin the grain boundary may be less than the amount of solid solution in amatrix after the brazing, and the values of S1/S2 and Z1/Z2 may be lessthan 1.00. Herein, the amount of solid solution in the vicinity of thegrain boundary is assumed to refer to the average value of the amountsof solid solution within a range of 0.05 μm on both sides of the grainboundary.

5. Recrystallization Temperature During Brazing

In the aluminum alloy fin material according to the present disclosure,a recrystallization temperature in a temperature rise process duringbrazing is set at 450° C. or less. Such limitations are intended toprevent a fin from being melted during brazing. The reasons of thelimitations will be described below.

As already mentioned, suppression of grain boundary segregation inrecrystallization during brazing is required for preventing a grainboundary from being melted during brazing. However, since Si and Zn incertain amounts form solid solution in a matrix, it is difficult tocompletely prevent grain boundary segregation occurring inrecrystallization. Even if grain boundary segregation occurs in such acase, a grain boundary is not melted when a time betweenrecrystallization and the melting of a brazing filler material duringbrazing is sufficient, and an element segregated in a grain boundaryduring the time diffuses into a matrix, thereby eliminating the grainboundary segregation. As a result of repeatedly conducting intensiveresearch with attention to the above, the present inventors found thatmelting of a grain boundary can be suppressed by eliminating grainboundary segregation before melting of a brazing-filler by completingrecrystallization early in a temperature rise process during brazing.

Specifically, the present inventors found that a recrystallizationtemperature of 450° C. or less in a temperature rise process duringbrazing results in elimination of grain boundary segregation beforemelting of a brazing-filler, thereby preventing a grain boundary frombeing melted. In other words, when a recrystallization temperature in atemperature rise process during brazing is 450° C. or less, both thevalues of S1/S2 and Z1/Z2 described above can be controlled to 1.20 orless, whereby grain boundary segregation during the brazing issufficiently suppressed, and a grain boundary is not melted. Incontrast, when a recrystallization temperature in a temperature riseprocess during brazing is more than 450° C., grain boundary segregationis not eliminated before melting of a brazing-filler, and a grainboundary is melted. In other words, when a recrystallization temperaturein a temperature rise process during brazing is more than 450° C., oneor both of the values of S1/S2 and Z1/Z2 described above are more than1.20, thereby resulting in insufficient suppression of grain boundarysegregation during the brazing and in melting of a grain boundary. Arecrystallization temperature in a temperature rise process duringbrazing is preferably 400° C. or less. The lower limit of arecrystallization temperature in a temperature rise process duringbrazing is not limited from the viewpoint of resistance to melting of afin, but it is difficult to set the lower limit at 250° C. or lessbecause thermal energy for causing recrystallization is insufficient inan excessively low temperature range in the aluminum alloy fin materialof the present disclosure.

Brazing heating conditions (brazing heating relevant conditions) are notparticularly limited, but brazing heating is performed at a heating rateof typically 60 to 160° C./min, preferably 80 to 140° C./min, in atemperature range of 300 to 580° C., for 2 to 10 minutes at anattainment temperature of 585 to 620° C., preferably for 2 to 6 minutesat an attainment temperature of 590 to 615° C. When a heating rate in atemperature range of 300 to 580° C. is less than 60° C./min, the heatingrate is too slow, and production efficiency is considerablydeteriorated. When the heating rate is more than 160° C./min, atemperature distribution during brazing may become nonuniform. Anattainment temperature of less than 585° C. may result in insufficientmelting of a brazing-filler and may prevent favorable brazing, while anattainment temperature of more than 620° C. may cause a material to bemelted. A brazed product is typically cooled at a cooling rate of 20 to500° C./min.

6. Methods of Producing Aluminum Alloy Fin Material

The aluminum alloy fin material according to the present disclosure canbe produced by production methods according to two differentembodiments. The production method in Embodiment 1 is characterized byincluding a hot-rolling step and a cold-rolling step, differs in thehot-rolling step from the production method in Embodiment 2 describedlater, further includes a homogenization treatment step as an optionalstep, and also differs in the conditions of the homogenization treatmentstep from the production method in Embodiment 2. In contrast, theproduction method in Embodiment 2 is characterized by including ahomogenization treatment step and a cold-rolling step, differs inincluding the homogenization treatment step as an essential step fromthe production method in Embodiment 1, and also differs in theconditions of the homogenization treatment step from the productionmethod in Embodiment 1. In addition, the hot-rolling step in theproduction method in Embodiment 2 differs from that in Embodiment 1.

6-1. Production Method in Embodiment 1

The method of producing the aluminum alloy fin material according to thepresent disclosure in Embodiment 1 will now be described.

6-1-1. Each Production Step

The method of producing the aluminum alloy fin material according to thepresent disclosure in Embodiment 1 includes a step of casting analuminum alloy, a hot-rolling step of hot-rolling a cast ingot, acold-rolling step of cold-rolling a hot-rolled sheet, and one or moreannealing steps of annealing a cold-rolled sheet in or after thecold-rolling step, or in and after the cold-rolling step.

In the aluminum alloy fin material of the present disclosure, excellentresistance to melting of a fin and high-temperature durability areachieved by controlling the amounts of solid solution Si and solidsolution Mn, and a recrystallization temperature during brazing. As aresult of intensive research, the present inventors found that in aproduction step, the hot-rolling step most greatly influences theamounts of solid solution Si and solid solution Mn, and the cold-rollingstep most greatly influences a recrystallization temperature duringbrazing. Methods of controlling the hot-rolling step and thecold-rolling step will be described below.

6-1-2. Hot-Rolling Step

The method of producing the aluminum alloy fin material according to thepresent disclosure in Embodiment 1 is characterized primarily by thehot-rolling step of hot-rolling a cast aluminum alloy ingot. Thehot-rolling step includes a heating stage of heating an ingot, aretention stage subsequent to the heating stage, and a hot-rolling stageof rolling the heated and retained ingot. In the heating stage, aheating rate from attainment of 400° C. to attainment of a retentiontemperature in the retention stage is set at 60° C./h or less. In theretention stage, the retention temperature is set at 450 to 560° C., anda retention time is set at 0.5 hour or more. Further, in the hot-rollingstage, a time for which the hot-rolled sheet has a temperature of 400°C. or more is set at 5 minutes or more. The setting of the conditions ofthe step of hot-rolling an aluminum alloy in such a manner enables thealuminum alloy fin material according to the present disclosure toachieve the amount of solid solution Si before brazing, set in thepresent disclosure, and the amounts of solid solution Mn before andafter the brazing, set in the present disclosure (hereinafter referredto as “amounts of solid solution Si and solid solution Mn set in thepresent disclosure”) and to exhibit excellent resistance to melting of afin and excellent high-temperature durability during the brazing. Thereasons thereof will be described below.

In the step of casting an aluminum alloy, large amounts of Si and Mnform solid solution in the matrix of the ingot. Such large amounts of Siand Mn forming solid solution in the matrix in such a manner generatethe nuclei of Al—Mn-based and Al—Mn—Si-based intermetallic compounds inthe heating stage prior to the rolling stage in the hot-rolling step,and in the rolling stage, a large amount of the intermetallic compoundsis precipitated based on the nuclei. As a result, the hot-rolling stepincluding the heating stage almost determines the amounts of solidsolution Si and solid solution Mn, set in the present disclosure, in thealuminum alloy fin material.

Therefore, in order to reduce the amounts of solid solution Si and solidsolution Mn, maximum amounts of the nuclei of Al—Mn-based andAl—Mn—Si-based intermetallic compounds may be generated in the heatingstage, and maximum amounts of the intermetallic compounds may beprecipitated in the rolling stage. In particular, because the amounts ofthe generated nuclei after attainment of 400° C. are large in theheating stage, subsequent temperature control is important. Al—Mn-basedand Al—Mn—Si-based intermetallic compounds can be sufficientlyprecipitated, and the amounts of solid solution Si and solid solutionMn, set in the present disclosure, can be obtained, by setting, at 60°C./h or less, a heating rate from attainment of 400° C. to attainment ofa retention temperature in the heating stage, setting, at 0.5 hour ormore, a retention time at a retention temperature of 450 to 560° C. inthe retention stage, and setting, at 5 minutes or more, a time for whichthe hot-rolled sheet has a temperature of 400° C. or more in thehot-rolling stage.

When the heating rate from the attainment of 400° C. to the attainmentof the retention temperature in the heating stage is more than 60° C./h,or when the retention time at a retention temperature of 450 to 560° C.in the retention stage is less than 0.5 hour, the amount of generatednuclei is insufficient, and it is impossible to obtain the amounts ofsolid solution Si and solid solution Mn, set in the present disclosure.When the time for which the hot-rolled sheet has a temperature of 400°C. or more is less than 5 minutes in the rolling stage, the amounts ofprecipitated Al—Mn-based and Al—Mn—Si-based intermetallic compounds areinsufficient, and it is impossible to obtain the amounts of solidsolution Si and solid solution Mn, set in the present disclosure. Whenthe retention temperature in the retention stage is more than 560° C.,the nuclei of the generated intermetallic compounds further dissolved,and it is impossible to obtain the amounts of solid solution Si andsolid solution Mn, set in the present disclosure. In addition, aretention temperature of more than 560° C. may cause the aluminum alloyto be melted, thereby preventing a fin material from being produced. Aretention temperature of less than 450° C. in the retention stage mayresult in insufficient plastic workability in the hot rolling, therebycausing cracking in the hot rolling and preventing an aluminum alloymaterial from being produced.

The heating rate from the attainment of 400° C. to the attainment of theretention temperature in the heating stage is preferably 50° C./h orless, the retention time in the retention stage is preferably 1.0 houror more, the retention temperature in the retention stage is preferably460 to 540° C., and the time for which the hot-rolled sheet has atemperature of 400° C. or more in the hot-rolling stage is preferably 7minutes or more.

The lower limit value of the heating rate from the attainment of 400° C.to the attainment of the retention temperature in the retention stage isnot particularly limited from the viewpoint of the amounts of solidsolution Si and solid solution Mn, set in the present disclosure, butwhen the lower limit value is set at less than 10° C./h, a very longtime is needed for rising a temperature, and economic efficiency isconsiderably deteriorated. The upper limit value of the retention timein the retention stage is not particularly limited from the viewpoint ofthe amounts of solid solution Si and solid solution Mn, set in thepresent disclosure, but when the upper limit value is more than 20hours, economic efficiency is considerably deteriorated. In addition,the upper limit value of the time for which the hot-rolled sheet has atemperature of 400° C. or more in the hot-rolling stage is notparticularly limited, but when the upper limit value is more than 50minutes, economic efficiency is considerably deteriorated.

6-1-3. Cold-Rolling Step

The method of producing the aluminum alloy fin material according to thepresent disclosure in Embodiment 1 is further characterized by thecold-rolling step. In the cold-rolling step, the temperature of thecold-rolled sheet is set at 120° C. or less. Such control can result ina decrease in recrystallization temperature during brazing, whereby arecrystallization temperature in a temperature rise process duringbrazing heating can be set at 450° C. or less, grain boundarysegregation is consequently eliminated before melting of abrazing-filler during the brazing, each of the values of S1/S2 and Z1/Z2further consequently becomes 1.20 or less, and melting of a fin can besuppressed. The reasons thereof will be described below.

As already mentioned, recrystallization occurs in an aluminum alloy finmaterial during brazing. Processing strain applied to the aluminum alloyduring cold rolling is driving force for the recrystallization. However,since heat is also generated due to processing during the cold rolling,only the cold rolling results in an increase in the temperature of amaterial due to the heat generated due to the processing, therebyrecovering the applied processing strain, and therefore results ininsufficient processing strain. As a result of repeatedly conductingintensive research with attention to the above, the present inventorsfound that when the temperature of the cold-rolled sheet during thecold-rolling step is 120° C. or less, sufficient processing strain canbe obtained, and a recrystallization temperature during brazing time canbe lowered to 450° C. or less.

When the temperature of the cold-rolled sheet during the cold rolling ismore than 120° C., the applied processing strain is recovered, and it isimpossible to lower a recrystallization temperature during brazing to450° C. or less. The temperature of the cold-rolled sheet during thecold rolling is preferably 100° C. or less. The lower limit value of thetemperature of the aluminum alloy during the cold rolling is not limitedfrom the viewpoint of processing strain, but it is difficult to set thelower limit value at 60° C. or less because it is impossible tocompletely eliminate heat generated due to processing. A method ofcontrolling the temperature of the aluminum alloy during the coldrolling is not particularly limited, but the temperature can becontrolled by, for example, a method in which a temperature in acold-rolling output side is measured and fed back into a cold-rollingrate.

When one or more annealing steps are performed in the cold rolling, theabove-described temperature control may be performed in final coldrolling after final annealing.

6-1-4. Other Steps

The step of casting the aluminum alloy fin material according to thepresent disclosure in Embodiment 1 is performed by a semi-continuouscasting (DC) method. In the aluminum alloy fin material according to thepresent disclosure, melting of a fin and rupture of the fin due tohigh-temperature fatigue are suppressed by the heating stage, theretention stage, and the hot-rolling stage in the hot-rolling step, asalready mentioned. Examples of the method of casting the aluminum alloyinclude a continuous casting method as well as the semi-continuouscasting method. However, an aluminum alloy obtained by the continuouscasting method has a small sheet thickness, is incapable of beingsubjected to the hot-rolling step, and is therefore incapable of beingapplied to the present disclosure.

The ingot obtained by casting the aluminum alloy may be subjected to thehomogenization treatment step before the hot-rolling step. Typically,the homogenization treatment step is preferably performed at 450 to 620°C. for 1 to 24 hours, and more preferably performed at 480 to 620° C.for 1 to 20 hours. A treatment temperature of less than 450° C. or atreatment time of less than 1 hour may result in an insufficienthomogenization effect, while a treatment temperature of more than 620°C. may cause the ingot to be melted. A treatment time of more than 24hours causes economic efficiency to be considerably deteriorated.Control equivalent to the already-mentioned control set in the heatingstage in the hot-rolling step can be performed in the heating stage inthe homogenization treatment step. However, when the aluminum alloy istemporarily cooled after the homogenization treatment, the nucleus of agenerated intermetallic compound disappears, and therefore, it isimpossible to obtain an effect equivalent to the effect of treatment inthe heating stage in the hot-rolling step.

The annealing step is performed one or more times in or after thecold-rolling step, or in and after the cold-rolling step for the purposeof improvement of formability, and the like. Specifically, (1)intermediate annealing is performed one or more times in thecold-rolling step, (2) a final annealing step is performed once afterthe cold-rolling step, or (3) (1) and (2) are performed. In theannealing step, a fin material is preferably retained at 200 to 450° C.for 1 to 10 hours. A retention temperature of less than 200° C. and aretention time of less than 1 hour may cause the above-described effectsto be insufficient. A retention temperature of more than 450° C. and aretention time of more than 10 hours cause economic efficiency to beconsiderably deteriorated. More preferred annealing conditions are atemperature of 230 to 420° C. and a retention time of 1 to 8 hours. Theupper limit of the number of such annealing steps is not particularlylimited, but the upper limit is preferably set at three in order toavoid an increase in cost due to the increased number of steps. When theannealing is performed in the cold rolling, a cold rolling reductionbetween the final annealing and the attainment of a final sheetthickness is preferably set at 15% or more from the viewpoint of thealready-mentioned processing strain.

6-2. Production Method in Embodiment 2

The method of producing the aluminum alloy fin material according to thepresent disclosure in Embodiment 2 will now be described.

6-2-1. Each Production Step

The method of producing the aluminum alloy fin material according to thepresent disclosure in Embodiment 2 includes a step of casting analuminum alloy, a homogenization treatment step ofhomogenization-treating a cast ingot, a hot-rolling step of hot-rollinga homogenization-treated ingot, a cold-rolling step of cold-rolling ahot-rolled sheet, and one or more annealing steps of annealing acold-rolled sheet in or after the cold-rolling step, or in and after thecold-rolling step.

In the aluminum alloy fin material of the present disclosure, excellentresistance to melting of a fin and high-temperature durability areachieved by controlling the amounts of solid solution Si and solidsolution Mn, and a recrystallization temperature during brazing. As aresult of intensive research, the present inventors found that in aproduction step, the homogenization treatment step most greatlyinfluences the amounts of solid solution Si and solid solution Mn, andthe cold-rolling step most greatly influences a recrystallizationtemperature during brazing. Methods of controlling the homogenizationtreatment step and the cold-rolling step will be described below.

6-2-2. Homogenization Treatment Step

The method of producing the aluminum alloy fin material according to thepresent disclosure in Embodiment 2 is characterized primarily by thehomogenization treatment step of homogenization-treating a cast aluminumalloy ingot. The homogenization treatment step includes a heating stageof heating an ingot, a retention stage subsequent to the heating stage,and a cooling stage of cooling the heated and retained ingot. In theheating stage, a heating rate from attainment of 400° C. to attainmentof a retention temperature in the retention stage is set at 60° C./h orless. In the retention stage, the retention temperature is set at 450 to560° C., and a retention time is set at 1.0 hour or more. Further, inthe cooling stage, a cooling rate before the ingot attains a temperatureof 400° C. is set at 60° C./h or less. The setting of the conditions ofthe step of homogenization-treating an aluminum alloy in such a mannerenables the aluminum alloy fin material according to the presentdisclosure to achieve the amount of solid solution Si before brazing,set in the present disclosure, and the amounts of solid solution Mnbefore and after the brazing, set in the present disclosure (hereinafterreferred to as “amounts of solid solution Si and solid solution Mn setin the present disclosure”) and to exhibit excellent resistance tomelting of a fin and excellent high-temperature durability during thebrazing. The reasons thereof will be described below.

In the step of casting an aluminum alloy, large amounts of Si and Mnform solid solution in the matrix of the ingot. Such large amounts of Siand Mn forming solid solution in the matrix in such a manner generateAl—Mn-based and Al—Mn—Si-based intermetallic compounds in the heatingstage, the retention stage, and the cooling stage in the homogenizationtreatment step, and the conditions of the homogenization treatment stepincluding the three stages almost determine the amounts of solidsolution Si and solid solution Mn, set in the present disclosure, in thealuminum alloy fin material before brazing.

Therefore, in order to reduce the amounts of solid solution Si and solidsolution Mn, maximum amounts of Al—Mn-based and Al—Mn—Si-basedintermetallic compounds may be precipitated in the heating stage, theretention stage, and the cooling stage. In particular, because aprecipitation amount in a temperature range of 400° C. or more is large,subsequent temperature control is important. Al—Mn-based andAl—Mn—Si-based intermetallic compounds can be sufficiently precipitated,and the amounts of solid solution Si and solid solution Mn, set in thepresent disclosure, can be obtained, by setting, at 60° C./h or less, aheating rate from attainment of 400° C. to attainment of a retentiontemperature in the heating stage, setting, at 1.0 hour or more, aretention time at a retention temperature of 450 to 560° C. in theretention stage, and setting, at 60° C./h or less, a cooling rate beforethe ingot attains a temperature of 400° C. in the cooling stage.

When the heating rate from the attainment of 400° C. to the attainmentof the retention temperature in the heating stage is more than 60° C./h,when in the retention stage, the retention temperature is less than 450°C. or the retention time is less than 1.0 hour, or when the cooling ratebefore the ingot attains a temperature of 400° C. in the cooling stageis more than 60° C./h, the amount of precipitated intermetallic compoundis insufficient, and it is impossible to obtain the amounts of solidsolution Si and solid solution Mn, set in the present disclosure. Whenthe retention temperature in the retention stage is more than 560° C.,Si and Mn in the precipitated intermetallic compounds further dissolved,and it is impossible to obtain the amounts of solid solution Si andsolid solution Mn, set in the present disclosure. In addition, aretention temperature of more than 560° C. may cause the aluminum alloyto be melted, thereby preventing a fin material from being produced.

The heating rate from the attainment of 400° C. to the attainment of theretention temperature in the heating stage is preferably 50° C./h orless, the retention time in the retention stage is preferably 2.0 hoursor more, the retention temperature in the retention stage is preferably480 to 530° C., and the cooling rate before the ingot attains atemperature of 400° C. in the cooling stage is preferably 50° C./h orless.

The lower limit values of the heating rate from the attainment of 400°C. in the heating stage to the attainment of the retention temperaturein the retention stage and the cooling rate before the ingot attains atemperature of 400° C. in the cooling stage are not particularly limitedfrom the viewpoint of the amounts of solid solution Si and solidsolution Mn, set in the present disclosure, but when the lower limitvalues are set at less than 10° C./h, very long times are needed forincreasing and decreasing temperatures, and economic efficiency isconsiderably deteriorated. The upper limit value of the retention timein the retention stage is not particularly limited from the viewpoint ofthe amounts of solid solution Si and solid solution Mn, defined in thepresent disclosure, but when the retention time is more than 20 hours,economic efficiency is considerably deteriorated.

6-2-3. Cold-Rolling Step

The method of producing the aluminum alloy fin material according to thepresent disclosure in Embodiment 2 is further characterized by thecold-rolling step. In the cold-rolling step, the temperature of thecold-rolled sheet is set at 120° C. or less. Such control can result ina decrease in recrystallization temperature during brazing, whereby arecrystallization temperature in a temperature rise process duringbrazing heating can be set at 450° C. or less, grain boundarysegregation is consequently eliminated before melting of abrazing-filler during the brazing, each of the values of S1/S2 and Z1/Z2further consequently becomes 1.20 or less, and melting of a fin can besuppressed. The reasons thereof will be described below.

As already mentioned, recrystallization occurs in an aluminum alloy finmaterial during brazing. Processing strain applied to the aluminum alloyduring cold rolling is driving force for the recrystallization. However,since heat is also generated due to processing during the cold rolling,only the cold rolling results in an increase in the temperature of amaterial due to the heat generated due to the processing, therebyrecovering the applied processing strain, and therefore results ininsufficient processing strain. As a result of repeatedly conductingintensive research with attention to the above, the present inventorsfound that when the temperature of the cold-rolled sheet during thecold-rolling step is 120° C. or less, sufficient processing strain canbe obtained, and a recrystallization temperature during brazing time canbe lowered to 450° C. or less.

When the temperature of the cold-rolled sheet during the cold rolling ismore than 120° C., the applied processing strain is recovered, and it isimpossible to lower a recrystallization temperature during brazing to450° C. or less. The temperature of the cold-rolled sheet during thecold rolling is preferably 100° C. or less. The lower limit value of thetemperature of the aluminum alloy during the cold rolling is not limitedfrom the viewpoint of processing strain, but it is difficult to set thelower limit value at 60° C. or less because it is impossible tocompletely eliminate heat generated due to processing. A method ofcontrolling the temperature of the aluminum alloy during the coldrolling is not particularly limited, but the temperature can becontrolled by, for example, a method in which a temperature in acold-rolling output side is measured and fed back to a cold-rollingrate.

When one or more annealing steps are performed in the cold rolling, theabove-described temperature control may be performed in final coldrolling after final annealing.

6-2-4. Other Steps

The step of casting the aluminum alloy fin material according to thepresent disclosure in Embodiment 2 is performed by a semi-continuouscasting (DC) method. In the aluminum alloy fin material according to thepresent disclosure, melting of a fin and rupture of the fin due tohigh-temperature fatigue are suppressed by the heating stage, theretention stage, and the cooling stage in the homogenization treatmentstep, as already mentioned. Examples of the method of casting thealuminum alloy include a continuous casting method as well as thesemi-continuous casting method. However, an aluminum alloy obtained bythe continuous casting method has a small sheet thickness, is incapableof being subjected to the hot-rolling step, and is therefore incapableof being applied to the present disclosure.

After the casting step, the ingot of the aluminum alloy subjected to thehomogenization treatment step is then subjected to the hot-rolling step.In the heating stage in the hot-rolling step, the ingot is preferablyheated at 400 to 580° C. for 0.5 hour or more, and more preferably at420 to 550° C. for 1 hour or more. A heating temperature of less than400° C. may result in low plastic workability and in cracking in the hotrolling, a heating temperature of more than 580° C. may cause the ingotto be melted, a heating time of less than 0.5 hour may result in thenonuniform temperature of the ingot. The upper limit value of theheating time is not particularly limited, but is around 20 hours in thepresent disclosure from the viewpoint of economic efficiency.

The annealing step is performed one or more times in or after thecold-rolling step, or in and after the cold-rolling step for the purposeof improvement of formability, and the like. Specifically, (1)intermediate annealing is performed one or more times in thecold-rolling step, (2) a final annealing step is performed once afterthe cold-rolling step, or (3) (1) and (2) are performed. In theannealing step, a fin material is preferably retained at 200 to 450° C.for 1 to 10 hours. A retention temperature of less than 200° C. and aretention time of less than 1 hour may cause the above-described effectsto be insufficient. A retention temperature of more than 450° C. and aretention time of more than 10 hours cause economic efficiency to beconsiderably deteriorated. More preferred annealing conditions are atemperature of 230 to 420° C. and a retention time of 1 to 8 hours. Theupper limit of the number of such annealing steps is not particularlylimited, but the upper limit is preferably set at three in order toavoid an increase in cost due to the increased number of steps. When theannealing is performed in the cold rolling, a cold rolling reductionbetween the final annealing and the attainment of a final sheetthickness is preferably set at 15% or more from the viewpoint of thealready-mentioned processing strain.

The sheet thickness of the aluminum alloy fin material according to thepresent disclosure is not particularly limited, but the aluminum alloyfin material sufficiently exhibits superiority in improvement inresistance to melting and improvement in high-temperature durabilitywhen being a thin-thickness material having a sheet thickness of 100 μmor less. A sheet thickness of more than 100 μm does not cause themelting and high-temperature durability of a fin to be very problematic,and therefore results in the insufficient exhibition of the superiorityof the present disclosure.

7. Heat Exchanger

The aluminum alloy fin material according to the present disclosure ispreferably used as a fin for a heat exchanger. A heat exchanger can beobtained by, for example, corrugating the aluminum alloy fin material ina fin shape, then combining the aluminum alloy fin material with amember for a heat exchange, such as a flow passage formation componentor a header plate, and subjecting the aluminum alloy fin material tobrazing heating.

The heat exchanger is assembled by arranging the fin materials on theouter surface of a flow passage formation component of which both endportions are attached to header plates. Then, both the overlapped endportions of the flow passage formation component, the fin material andthe outer surface of the flow passage formation component, and both endsof the flow passage formation component and the header plates aresimultaneously joined to each other by one-time brazing heating. As abrazing method, a fluxless brazing method, a Nocolok brazing method, ora vacuum brazing method is used, and the Nocolok brazing method ispreferred. In such brazing, a recrystallization temperature in atemperature rise process during brazing is set at 450° C. or less inorder to prevent a fin from being melted during the brazing, asdescribed above. The other brazing heating conditions are preferably thesame as described above.

EXAMPLES

The present disclosure will now be described in more detail withreference to present disclosure examples and comparative examples.However, the present disclosure is not restricted thereto.

Example 1 (Present Disclosure Examples 1-1 to 1-9, and 1-19 to 1-28, andComparative Examples 1-10 to 1-18, and 1-29 to 1-34)

The aluminum alloy fin material produced by the production method ofEmbodiment 1 will now be described.

Each of aluminum alloys with alloy compositions shown in Table 1 wascast by DC casting, and both surfaces of each of the aluminum alloyswere faced and finished. All the thicknesses of the ingots obtained bythe facing were set at 400 mm. Each of the ingots of the aluminum alloyswas subjected to a homogenization treatment step, a hot-rolling step, acold-rolling step, and an annealing step under conditions shown in Table2. All the sheet thicknesses after the hot rolling were 3 mm. Then, afin material sample having a final sheet thickness of 0.05 mm wasproduced in any one of (1) order of cold rolling→intermediateannealing→final cold rolling, (2) order of cold rolling→intermediateannealing→final cold rolling→final annealing, and (3) order of coldrolling→final annealing. All the conditions of the intermediateannealing and the final annealing were set at 370° C. and 2 hours, andall the rolling reductions in the final cold rolling after theintermediate annealing was set at 30%. The combinations of the steps areshown in Table 2.

TABLE 1 Alloy Alloy composition (mass %) designation Si Fe Cu Mn Zn TiZr Cr V Al A1 0.90 0.20 — 1.4 2.0 — — — — Bal. Within the A2 0.70 0.20 —1.4 2.0 0.05 — — — Bal. scope of A3 1.50 0.20 — 1.4 2.0 — 0.05 — — Bal.the present A4 0.90 0.05 0.05 1.4 2.0 — — 0.05 — Bal. disclosure A5 0.902.00 0.30 1.4 2.0 — — — 0.05 Bal. A6 0.90 0.20 — 1.0 2.0 0.30 0.30 0.300.30 Bal. A7 0.90 0.20 — 2.0 2.0 — — — — Bal. A8 0.90 0.20 — 1.4 0.5 — —— — Bal. A9 0.90 0.20 — 1.4 4.0 — — — — Bal. A10 0.60 0.20 — 1.4 2.0 — —— — Bal. Outside the A11 1.60 0.20 — 1.4 2.0 — 0.15 — — Bal. scope ofA12 0.90 2.20 — 1.4 2.0 0.15 0.15 — — Bal. the present A13 0.90 0.20 —0.9 2.0 — — — — Bal. disclosure A14 0.90 0.20 — 2.2 2.0 — — — — Bal. A150.90 0.20 0.40 1.4 2.0 — — — — Bal. A16 0.90 0.20 — 1.4 2.0 0.40 0.400.40 0.40 Bal. A17 0.90 0.20 — 1.4 0.4 — — — — Bal. A18 0.90 0.20 — 1.44.5 — — — — Bal.

TABLE 2 Hot-rolling step Heating stage heating rate (° C./h)Homogenization from attainment Hot-rolling stage treatment step of 400°C. to Time Steps Temperature Retention Retention attainment of Retentionstage Start (min) at performed (° C.) during Production temperature timeretention Temperature Time temperature 400° C. after cold final colddesignation (° C.) (h) temperature (° C.) (h) (° C.) or more rollingrolling B1-1 N/A 40 500 3 490 10 (1) 100 Within the B1-2 N/A 10 500 3490 10 (2) 100 scope of B1-3 N/A 60 500 3 490 10 (3) 120 the presentB1-4 N/A 40 450 3 440 10 (1) 100 disclosure B1-5 N/A 40 560 3 550 10 (1)100 B1-6 N/A 40 500 0.5 490 10 (1) 100 B1-7 N/A 40 500 20 490 10 (1) 100B1-8 N/A 40 500 3 490 5 (1) 100 B1-9 N/A 40 500 3 490 30 (1) 100 B1-10450 1 40 500 3 490 10 (1) 100 B1-11 620 20 40 500 3 490 10 (1) 100 B1-12N/A 70 500 3 490 10 (1) 80 Outside the B1-13 N/A 40 440 3 430 10 (1) 100scope of B1-14 N/A 40 570 3 430 10 (1) 100 the present B1-15 N/A 40 5000.3 490 10 (1) 100 disclosure B1-16 N/A 40 500 3 490 3 (1) 100 B1-17 N/A40 500 3 490 10 (1) 130

In Table 3, productability is shown as “good” in a case in which noproblem occurred in the above production steps, and rolling was able tobe performed up to a final sheet thickness of 0.05 mm, whileproductability is shown as “poor” in a case in which cracking occurredduring casting or rolling, and rolling was not able to be performed upto a final sheet thickness of 0.05 mm, or in a case in which meltingoccurred in the homogenization treatment step, and a fin material wasnot able to be produced.

The above-described fin material samples were subjected to each of thefollowing evaluations. The conditions of brazing heating (brazingheating relevant conditions) in the evaluations are shown in Table 4,and the evaluation results are shown in Table 3. The samples withproductability “poor” in Table 3 were not able to be produced, andtherefore, were not able to be subjected to the following evaluations.

TABLE 3 High-temperature fatigue life after brazing heating Tensilestrength The number after brazing heating of times of Measurementrepetition before Alloy Production Brazing value rupture × 10⁶designation designation Productability condition Brazability (MPa)Determination (times) Present 1-1 A1 B1-1 Good C1 Good 141 Good 1.67Disclosure 1-2 A2 B1-1 Good C2 Good 136 Good 1.52 Examples 1-3 A3 B1-1Good C3 Good 157 Good 1.94 1-4 A4 B1-1 Good C4 Good 141 Good 1.56 1-5 A5B1-1 Good C5 Good 161 Good 2.33 1-6 A6 B1-1 Good C1 Good 138 Good 2.691-7 A7 B1-1 Good C1 Good 146 Good 1.43 1-8 A8 B1-1 Good C1 Good 141 Good1.71 1-9 A9 B1-1 Good C1 Good 142 Good 1.75 Comparative 1-10 A10 B1-1Good C1 Good 122 Poor 1.71 Examples 1-11 A11 B1-1 Good C1 Poor 159 Good2.00 1-12 A12 B1-1 Poor — — — — — 1-13 A13 B1-1 Good C1 Good 126 Poor3.33 1-14 A14 B1-1 Poor — — — — — 1-15 A15 B1-1 Good C1 Good 153 Good1.84 1-16 A16 B1-1 Poor — — — — — 1-17 A17 B1-1 Good C1 Good 142 Good1.75 1-18 A18 B1-1 Good C1 Good 140 Good 1.67 Present 1-19 A1 B1-2 GoodC1 Good 138 Good 2.26 Disclosure 1-20 A1 B1-3 Good C1 Good 143 Good 1.19Examples 1-21 A1 B1-4 Good C1 Good 149 Good 1.35 1-22 A1 B1-5 Good C1Good 136 Good 2.19 1-23 A1 B1-6 Good C1 Good 145 Good 1.23 1-24 A1 B1-7Good C1 Good 140 Good 2.12 1-25 A1 B1-8 Good C1 Good 145 Good 1.59 1-26A1 B1-9 Good C1 Good 139 Good 1.25 1-27 A1 B1-10 Good C1 Good 139 Good1.71 1-28 A1 B1-11 Good C1 Good 137 Good 2.12 Comparative 1-29 A1 B1-12Good C1 Poor 149 Good 0.98 Examples 1-30 A1 B1-13 Good C1 Poor 150 Good0.92 1-31 A1 B1-14 Good C1 Poor 141 Good 0.94 1-32 A1 B1-15 Good C1 Poor135 Good 0.97 1-33 A1 B1-16 Good C1 Poor 142 Good 0.98 1-34 A1 B1-17Good C1 Poor 141 Good 1.30 Amount of solid Amount of solidHigh-temperature solution Si solution Mn Grain fatigue life after (mass%) (mass %) boundary Recrystallization brazing heating Before AfterBefore After segregation temperature Corrosion Determination brazingbrazing brazing brazing S1/S2 Z1/Z2 during brazing resistance Present1-1 Good 0.42 0.51 0.31 0.42 1.01 1.01 Good Good Disclosure 1-2 Good0.31 0.41 0.38 0.46 0.91 1.02 Good Good Examples 1-3 Good 0.50 0.52 0.260.36 1.02 1.01 Good Good 1-4 Good 0.45 0.53 0.41 0.45 1.05 1.11 GoodGood 1-5 Good 0.36 0.45 0.21 0.30 1.09 1.02 Good Good 1-6 Good 0.45 0.520.20 0.26 0.81 0.82 Good Good 1-7 Good 0.31 0.40 0.45 0.49 0.96 0.99Good Good 1-8 Good 0.40 0.50 0.31 0.41 0.92 0.93 Good Good 1-9 Good 0.410.50 0.32 0.40 1.01 1.03 Good Good Comparative 1-10 Good 0.21 0.32 0.360.41 1.05 1.05 Good Good Examples 1-11 Good 0.52 0.55 0.28 0.35 1.081.11 Good Good 1-12 — — — — — — — — — 1-13 Good 0.39 0.46 0.12 0.21 1.081.02 Good Good 1-14 — — — — — — — — — 1-15 Good 0.41 0.51 0.31 0.38 1.001.04 Good Poor 1-16 — — — — — — — — — 1-17 Good 0.40 0.50 0.31 0.40 1.070.99 Good Poor 1-18 Good 0.39 0.51 0.32 0.42 1.01 0.95 Good Poor Present1-19 Good 0.21 0.32 0.20 0.31 0.52 0.55 Good Good Disclosure 1-20 Good0.59 0.59 0.55 0.59 1.01 0.95 Good Good Examples 1-21 Good 0.59 0.550.57 0.52 1.03 1.05 Good Good 1-22 Good 0.31 0.42 0.22 0.32 1.11 1.04Good Good 1-23 Good 0.57 0.58 0.58 0.57 1.05 1.02 Good Good 1-24 Good0.31 0.45 0.25 0.33 0.92 0.95 Good Good 1-25 Good 0.30 0.39 0.32 0.440.99 0.96 Good Good 1-26 Good 0.57 0.58 0.55 0.56 1.02 1.01 Good Good1-27 Good 0.41 0.51 0.32 0.41 0.96 0.92 Good Good 1-28 Good 0.31 0.420.21 0.33 0.95 0.91 Good Good Comparative 1-29 Poor 0.62 0.61 0.61 0.611.11 1.12 Good Good Examples 1-30 Poor 0.63 0.61 0.63 0.65 1.05 1.11Good Good 1-31 Poor 0.62 0.65 0.61 0.64 1.15 0.96 Good Good 1-32 Poor0.66 0.61 0.67 0.62 1.01 0.99 Good Good 1-33 Poor 0.62 0.68 0.62 0.611.02 0.94 Good Good 1-34 Good 0.41 0.50 0.41 0.46 1.22 1.23 Poor Good

TABLE 4 heating rate at Attainment 300 to 580° C. temperature (° C./min)(° C.) C1 120 600 C2 60 600 C3 160 600 C4 120 585 C5 120 620

(Evaluation of Brazability)

Each fin material sample was corrugated to form a heat exchanger fin.The fin was combined with a brazing filler material surface of amaterial equivalent to a tube, which was obtained by cladding an A3003alloy core material with 10% of A4045 alloy and had a sheet thickness of0.3 mm, and dipped in 5% of fluoride flux suspension with water,subjected to brazing heating under any of the conditions of Table 4, toproduce a mini-core sample. The brazability of such a mini-core samplein which a fin was not melted was evaluated as acceptable (good), whilethe brazability of such a mini-core sample in which a fin was melted wasevaluated as unacceptable (poor).

(Measurement of Tensile Strength after Brazing Heating)

A sample solely of fin material was subjected to brazing relevantheating under any of the conditions of Table 4, and was subjected to atensile test according to JIS Z2241 under conditions of a tension speedof 10 min/min and a gauge length of 50 mm. Tensile strength was readfrom an obtained stress-strain curve. As a result, the case of a tensilestrength of 130 MPa or more was evaluated as acceptable (good), whilethe case of a tensile strength of less than 130 MPa was evaluated asunacceptable (poor).

(Measurement of High-Temperature Fatigue Life after Brazing Heating)

A sample solely of fin material was subjected to brazing relevantheating under any of the conditions of Table 4, and was subjected to afatigue test according to JIS Z2273 in a constant-temperature bathhaving a temperature of 100° C. A stress ratio was set at 0.1, a maximumstress was set at 100 MPa, and a frequency was set at 20 Hz. A case inwhich the number of times of repetition before rupture was 10⁶ or morewas evaluated as acceptable (good), while a case in which the number oftimes of repetition before rupture was less than 10⁶ was evaluated asunacceptable (poor).

(Measurement of Amount of Solid Solution Si and Amount of Solid SolutionMn)

A sample solely of fin material was subjected to brazing relevantheating under any of the conditions of Table 4. The sample subjected tothe brazing relevant heating and a sample subjected to no brazingrelevant heating were used as test samples, and were dissolved in phenolsolutions, and the samples, from which undissolved intermetalliccompounds were removed by filtration, were subjected to emissionspectrometry, thereby performing measurement. A value was determined asthe amount of solid solution of each of Si and Mn by subtracting theamount of each of Si and Mn existing as an intermetallic compound fromthe content of each of Si and Mn.

(Determination of Recrystallization Temperature During Brazing Heating)

A sample solely of fin material was heated under any of the conditionsof Table 4, taken out when the fin material sample had 450° C. intemperature rise, and subjected to a tensile test according to JIS Z2241under conditions of a tension speed of 10 mm/min and a gauge length of50 mm. A 0.2% proof stress was read from an obtained stress-straincurve, and a case in which the value of the 0.2% proof stress was 80 MPaor less resulted in a determination that recrystallization had beencompleted, and was evaluated as acceptable (good), while a case in whichthe value was more than 80 MPa resulted in a determination thatrecrystallization had not been completed, and was evaluated asunacceptable (poor).

(Evaluation of Grain Boundary Segregation)

A sample solely of fin material was subjected to brazing relevantheating under any of the conditions of Table 4. The sample subjected tothe brazing relevant heating and a sample subjected no brazing relevantheating were used as test samples, and were sampled to have a size of 20μm×20 μm with FIB (focused ion beam) so that a grain boundary wasincluded. In the sample, Si and Zn were mapped in a visual field of 0.2μm×0.2 μm by energy dispersive X-ray analysis (EDS) using a transmissionscanning electron microscope (STEM). On the basis of the results of themapping, the average values of the semi-quantitative values of theconcentration of Si and Zn within a range of 0.05 μm on both sides of agrain boundary were determined as S1 and Z1, respectively. In addition,the average values of the semi-quantitative values of the concentrationsof Si and Zn in a matrix were determined as S2 and Z2, respectively, andthe values of S1/S2 and Z1/Z2 were calculated.

(Evaluation of Corrosion Resistance by Measurement of Depth ofCorrosion)

A mini-core sample similar to the mini-core sample used for evaluatingthe brazability was produced, and was subjected to a SWAAT test on thebasis of ASTM-G85. A sample in which corrosion penetration did not occurin a material equivalent to a tube for 1000 hours was evaluated asacceptable (good), while a sample in which corrosion penetrationoccurred was evaluated as unacceptable (poor).

In Present Disclosure Examples 1-1 to 1-9 and 1-19 to 1-28, theconditions set in the present disclosure were satisfied, and all ofproductability, brazability, tensile strength after brazing heating,high-temperature fatigue life after the brazing heating, and corrosionresistance were acceptable.

In contrast, Comparative Example 1-10 resulted in unacceptable tensilestrength after brazing heating because of an excessively small amount ofSi composition.

Comparative Example 1-11 resulted in melting of a fin material duringbrazing and in unacceptable brazability because of an excessively largeamount of Si composition.

Comparative Example 1-12 resulted in cracking in rolling, in impossibleproduction of a fin material, and in unacceptable productability becauseof an excessively large amount of Fe composition.

Comparative Example 1-13 resulted in unacceptable tensile strength afterbrazing heating because of an excessively small amount of Mncomposition.

Comparative Example 1-14 resulted in cracking in rolling, in impossibleproduction of a fin material, and in unacceptable productability becauseof an excessively large amount of Mn composition.

Comparative Example 1-15 resulted in unacceptable corrosion resistancebecause of an excessively large amount of Cu composition.

Comparative Example 1-16 resulted in cracking in rolling, in impossibleproduction of a fin material, and in unacceptable productability becauseof excessively large amounts of Ti, Zr, Cr, and V compositions.

Comparative Example 1-17 resulted in unacceptable corrosion resistancebecause of an excessively small amount of Zn composition.

Comparative Example 1-18 resulted in unacceptable corrosion resistancebecause of an excessively large amount of Zn composition.

Comparative Example 1-29 resulted in an excessively large amount ofsolid solution Si before and after brazing, thereby causing melting ofthe grain boundary of a fin material during the brazing and resulting inunacceptable brazability, and resulted in an excessively large amount ofMn before and after the brazing, thereby also resulting in unacceptablehigh-temperature fatigue life, because of an excessively high heatingrate from attainment of 400° C. to attainment of a retention temperaturein a heating stage in a hot-rolling step.

Comparative Example 1-30 resulted in an excessively large amount ofsolid solution Si before and after brazing, thereby causing melting ofthe grain boundary of a fin material during the brazing and resulting inunacceptable brazability, and resulted in an excessively large amount ofMn before and after the brazing, thereby also resulting in unacceptablehigh-temperature fatigue life, because of an excessively low retentiontemperature in a retention stage in a hot-rolling step.

Comparative Example 1-31 resulted in an excessively large amount ofsolid solution Si before and after brazing, thereby causing melting ofthe grain boundary of a fin material during the brazing and resulting inunacceptable brazability, and resulted in an excessively large amount ofMn before and after the brazing, thereby also resulting in unacceptablehigh-temperature fatigue life, because of an excessively high retentiontemperature in a retention stage in a hot-rolling step.

Comparative Example 1-32 resulted in an excessively large amount ofsolid solution Si before and after brazing, thereby causing melting ofthe grain boundary of a fin material during the brazing and resulting inunacceptable brazability, and resulted in an excessively large amount ofMn before and after the brazing, thereby also resulting in unacceptablehigh-temperature fatigue life, because of an excessively short retentiontime in a retention stage in a hot-rolling step.

Comparative Example 1-33 resulted in an excessively large amount ofsolid solution Si before and after brazing, thereby causing melting ofthe grain boundary of a fin material during the brazing and resulting inunacceptable brazability, and resulted in an excessively large amount ofMn before and after the brazing, thereby also resulting in unacceptablehigh-temperature fatigue life, because of an excessively short time forwhich a temperature of 400° C. or more was achieved in a hot-rollingstage in a hot-rolling step.

Comparative Example 1-34 resulted in a recrystallization temperature ofmore than 450° C. during brazing, thereby failing to eliminate grainboundary segregation of Si and Zn occurring during the brazing,resulting in the excessively high values of S1/S2 and Z1/Z2, causingmelting of the grain boundary of a fin material during the brazing, andresulting in unacceptable brazability, because of the excessively hightemperature of a cold-rolled sheet in a cold-rolling step.

Example 2 (Present Disclosure Examples 2-1 to 2-9, and 2-19 to 2-26, andComparative Examples 2-10 to 2-18, and 2-27 to 2-32)

The aluminum alloy fin material produced by the production method ofEmbodiment 2 will now be described.

Each of aluminum alloys with alloy compositions shown in Table 1 asdescribed above was cast by DC casting, and both surfaces of each of thealuminum alloys were faced and finished. All the thicknesses of theingots obtained by the facing were set at 400 mm. Each of the ingots ofthe aluminum alloys was subjected to a homogenization treatment step, ahot-rolling step, a cold-rolling step, and an annealing step underconditions shown in Table 5. The homogenization-treated ingot was heatedat 480° C. for 3 hours in a heating stage in the hot-rolling step, andthen subjected to a hot-rolling stage to obtain a hot-rolled sheethaving a sheet thickness of 3 mm. Then, a fin material sample having afinal sheet thickness of 0.05 mm was produced in any one of (1) order ofcold rolling→intermediate annealing→final cold rolling, (2) order ofcold rolling→intermediate annealing→final cold rolling→final annealing,and (3) order of cold rolling→final annealing. All the conditions of theintermediate annealing and the final annealing were set at 370° C. and 2hours, and all the rolling reductions in the final cold rolling afterthe intermediate annealing was set at 30%. The combinations of the stepsare shown in Table 5.

TABLE 5 Homogenization treatment step Heating stage heating rate (°C./h) Cooling stage from attainment of 400° C. Retention stage Coolingrate before Steps performed Temperature (° C.) Production to attainmentof retention Temperature Time attainment of 400° C. after cold duringfinal cold designation temperature (° C.) (h) (° C./h) rolling rollingB2-1 40 500 3 10 (1) 100 Within the scope B2-2 10 500 3 10 (2) 100 ofthe present B2-3 60 500 3 10 (3) 120 disclosure B2-4 40 450 3 10 (1) 100B2-5 40 560 3 10 (1) 100 B2-6 40 500 1 10 (1) 100 B2-7 40 500 20 10 (1)100 B2-8 40 500 3 10 (1) 100 B2-9 40 500 3 60 (1) 100 B2-10 70 500 3 10(1) 80 Outside the scope B2-11 40 440 3 10 (1) 100 of the present B2-1240 570 3 10 (1) 100 disclosure B2-13 40 500 0.5 10 (1) 100 B2-14 40 5003 70 (1) 100 B2-15 40 500 3 10 (1) 130

In Table 6, productability is shown as “good” in a case in which noproblem occurred in the above production steps, and rolling was able tobe performed up to a final sheet thickness of 0.05 mm, whileproductability is shown as “poor” in a case in which cracking occurredduring casting or rolling, and rolling was not able to be performed upto a final sheet thickness of 0.05 mm, or in a case in which meltingoccurred in the homogenization treatment step, and a fin material wasnot able to be produced.

The above-described fin material samples were subjected to each of thefollowing evaluations. The conditions of brazing heating (brazingheating relevant conditions) in the evaluations are shown in Table 4 asdescribed above, and the evaluation results are shown in Table 6. Thesamples with productability “poor” in Table 6 were not able to beproduced, and therefore, were not able to be subjected to the followingevaluations.

TABLE 6 High-temperature fatigue life after brazing heating Tensilestrength The number after brazing heating of times of Measurementrepetition before Alloy Production Brazing value rupture × 10⁶designation designation Productability condition Brazability (MPa)Determination (times) Present 2-1 A1 B2-1 Good C1 Good 141 Good 1.67Disclosure 2-2 A2 B2-1 Good C2 Good 136 Good 1.52 Examples 2-3 A3 B2-1Good C3 Good 157 Good 1.94 2-4 A4 B2-1 Good C4 Good 141 Good 1.56 2-5 A5B2-1 Good C5 Good 161 Good 2.33 2-6 A6 B2-1 Good C1 Good 138 Good 2.692-7 A7 B2-1 Good C1 Good 146 Good 1.43 2-8 A8 B2-1 Good C1 Good 140 Good1.71 2-9 A9 B2-1 Good C1 Good 142 Good 1.75 Comparative 2-10 A10 B2-1Good C1 Good 122 Poor 1.71 Examples 2-11 A11 B2-1 Good C1 Poor 159 Good2.00 2-12 A12 B2-1 Poor — — — — — 2-13 A13 B2-1 Good C1 Good 126 Poor3.33 2-14 A14 B2-1 Poor — — — — — 2-15 A15 B2-1 Good C1 Good 153 Good1.84 2-16 A16 B2-1 Poor — — — — — 2-17 A17 B2-1 Good C1 Good 142 Good1.75 2-18 A18 B2-1 Good C1 Good 142 Good 1.67 Present 2-19 A1 B2-2 GoodC1 Good 138 Good 2.26 Disclosure 2-20 A1 B2-3 Good C1 Good 143 Good 1.19Examples 2-21 A1 B2-4 Good C1 Good 149 Good 1.35 2-22 A1 B2-5 Good C1Good 136 Good 2.19 2-23 A1 B2-6 Good C1 Good 145 Good 1.23 2-24 A1 B2-7Good C1 Good 140 Good 2.12 2-25 A1 B2-8 Good C1 Good 145 Good 1.59 2-26A1 B2-9 Good C1 Good 139 Good 1.25 Comparative 2-27 A1 B2-10 Good C1Poor 149 Good 0.98 Examples 2-28 A1 B2-11 Good C1 Poor 150 Good 0.922-29 A1 B2-12 Good C1 Poor 141 Good 0.94 2-30 A1 B2-13 Good C1 Poor 135Good 0.97 2-31 A1 B2-14 Good C1 Poor 142 Good 0.98 2-32 A1 B2-15 Good C1Poor 141 Good 1.30 Amount of solid Amount of solid High-temperaturesolution Si solution Mn Grain fatigue life after (mass %) (mass %)boundary Recrystallization brazing heating Before After Before Aftersegregation temperature Corrosion Determination brazing brazing brazingbrazing S1/S2 Z1/Z2 during brazing resistance Present 2-1 Good 0.42 0.510.31 0.42 1.01 1.01 Good Good Disclosure 2-2 Good 0.31 0.41 0.38 0.460.91 1.02 Good Good Examples 2-3 Good 0.50 0.52 0.26 0.36 1.02 1.01 GoodGood 2-4 Good 0.45 0.53 0.41 0.45 1.05 1.11 Good Good 2-5 Good 0.36 0.450.21 0.30 1.09 1.02 Good Good 2-6 Good 0.45 0.52 0.20 0.26 0.81 0.82Good Good 2-7 Good 0.31 0.40 0.45 0.49 0.96 0.99 Good Good 2-8 Good 0.400.50 0.31 0.41 0.92 0.93 Good Good 2-9 Good 0.41 0.50 0.32 0.40 1.011.03 Good Good Comparative 2-10 Good 0.21 0.32 0.36 0.41 1.05 1.05 GoodGood Examples 2-11 Good 0.52 0.55 0.28 0.35 1.08 1.11 Good Good 2-12 — —— — — — — — — 2-13 Good 0.39 0.46 0.12 0.21 1.08 1.02 Good Good 2-14 — —— — — — — — — 2-15 Good 0.41 0.51 0.31 0.38 1.00 1.04 Good Poor 2-16 — —— — — — — — — 2-17 Good 0.40 0.50 0.31 0.40 1.07 0.99 Good Poor 2-18Good 0.39 0.51 0.32 0.42 1.01 0.95 Good Poor Present 2-19 Good 0.21 0.320.20 0.31 0.52 0.55 Good Good Disclosure 2-20 Good 0.59 0.59 0.55 0.591.01 0.95 Good Good Examples 2-21 Good 0.59 0.55 0.57 0.52 1.03 1.05Good Good 2-22 Good 0.31 0.42 0.22 0.32 1.11 1.04 Good Good 2-23 Good0.57 0.58 0.58 0.57 1.05 1.02 Good Good 2-24 Good 0.31 0.45 0.25 0.330.92 0.95 Good Good 2-25 Good 0.30 0.39 0.32 0.44 0.99 0.96 Good Good2-26 Good 0.57 0.58 0.55 0.56 1.02 1.01 Good Good Comparative 2-27 Poor0.62 0.61 0.61 0.61 1.11 1.12 Good Good Examples 2-28 Poor 0.63 0.610.63 0.65 1.05 1.11 Good Good 2-29 Poor 0.62 0.65 0.61 0.64 1.15 0.96Good Good 2-30 Poor 0.66 0.61 0.67 0.62 1.01 0.99 Good Good 2-31 Poor0.62 0.68 0.62 0.61 1.02 0.94 Good Good 2-32 Good 0.41 0.50 0.41 0.461.22 1.23 Poor Good

Evaluation of brazability, measurement of tensile strength after brazingheating, measurement of high-temperature fatigue life after the brazingheating, measurement of the amount of solid solution Si and the amountof solid solution Mn, determination of a recrystallization temperatureduring the brazing heating, evaluation of grain boundary segregation,and evaluation of corrosion resistance by measurement of the depth ofcorrosion were performed in the same manners as the manners of Example1.

In Present Disclosure Examples 2-1 to 2-9, and 2-19 to 2-26, theconditions set in the present disclosure were satisfied, and all ofproductability, brazability, tensile strength after brazing heating,high-temperature fatigue life after the brazing heating, and corrosionresistance were acceptable.

In contrast, Comparative Example 2-10 resulted in unacceptable tensilestrength after brazing heating because of an excessively small amount ofSi composition.

Comparative Example 2-11 resulted in melting of a fin material duringbrazing and in unacceptable brazability because of an excessively largeamount of Si composition.

Comparative Example 2-12 resulted in cracking in rolling, in impossibleproduction of a fin material, and in unacceptable productability becauseof an excessively large amount of Fe composition.

Comparative Example 2-13 resulted in unacceptable tensile strength afterbrazing heating because of an excessively small amount of Mncomposition.

Comparative Example 2-14 resulted in cracking in rolling, in impossibleproduction of a fin material, and in unacceptable productability becauseof an excessively large amount of Mn composition.

Comparative Example 2-15 resulted in unacceptable corrosion resistancebecause of an excessively large amount of Cu composition.

Comparative Example 2-16 resulted in cracking in rolling, in impossibleproduction of a fin material, and in unacceptable productability becauseof excessively large amounts of Ti, Zr, Cr, and V compositions.

Comparative Example 2-17 resulted in unacceptable corrosion resistancebecause of an excessively small amount of Zn composition.

Comparative Example 2-18 resulted in unacceptable corrosion resistancebecause of an excessively large amount of Zn composition.

Comparative Example 2-27 resulted in an excessively large amount ofsolid solution Si before and after brazing, and an excessively largeamount of solid solution Si before and after brazing, thereby causingmelting of the grain boundary of a fin material during the brazing andresulting in unacceptable brazability, and resulted in an excessivelylarge amount of Mn before and after the brazing, thereby also resultingin unacceptable high-temperature fatigue life, because of an excessivelyhigh heating rate from attainment of 400° C. to attainment of aretention temperature in a heating stage in a homogenization treatmentstep.

Comparative Example 2-28 resulted in an excessively large amount ofsolid solution Si before and after brazing, thereby causing melting ofthe grain boundary of a fin material during the brazing and resulting inunacceptable brazability, and resulted in an excessively large amount ofMn before and after the brazing, thereby also resulting in unacceptablehigh-temperature fatigue life, because of an excessively low retentiontemperature in a retention stage in a homogenization treatment step.

Comparative Example 2-29 resulted in an excessively large amount ofsolid solution Si before and after brazing, thereby causing melting ofthe grain boundary of a fin material during the brazing and resulting inunacceptable brazability, and resulted in an excessively large amount ofMn before and after the brazing, thereby also resulting in unacceptablehigh-temperature fatigue life, because of an excessively high retentiontemperature in a retention stage in a homogenization treatment step.

Comparative Example 2-30 resulted in an excessively large amount ofsolid solution Si before and after brazing, thereby causing melting ofthe grain boundary of a fin material during the brazing and resulting inunacceptable brazability, and resulted in an excessively large amount ofMn before and after the brazing, thereby also resulting in unacceptablehigh-temperature fatigue life, because of an excessively short retentiontime in a retention stage in a homogenization treatment step.

Comparative Example 2-31 resulted in an excessively large amount ofsolid solution Si before and after brazing, thereby causing melting ofthe grain boundary of a fin material during the brazing and resulting inunacceptable brazability, and resulted in an excessively large amount ofMn before and after the brazing, thereby also resulting in unacceptablehigh-temperature fatigue life, because of an excessively high coolingrate before the temperature of an ingot attained 400° C. in a coolingstage, in a hot-rolling stage in a homogenization treatment step.

Comparative Example 2-32 resulted in a recrystallization temperature ofmore than 450° C. during brazing, thereby failing to eliminate grainboundary segregation of Si and Zn occurring during the brazing,resulting in the excessively high values of S1/S2 and Z1/Z2, causingmelting of the grain boundary of a fin material during the brazing, andresulting in unacceptable brazability, because of the excessively hightemperature of a cold-rolled sheet in a cold-rolling step.

INDUSTRIAL APPLICABILITY

The aluminum alloy fin material according to the present disclosure ispreferably used particularly as a fin material for an automotive heatexchanger because of being excellent in strength, corrosion resistance,and brazability such as a joining rate and resistance to melting inbrazing.

1. An aluminum alloy fin material for a heat exchanger, the aluminumalloy fin material comprising an aluminum alloy comprising 0.70 to 1.50mass % Si, 0.05 to 2.00 mass % Fe, 1.0 to 2.0 mass % Mn, 0.5 to 4.0 mass% Zn, with a balance consisting of Al and inevitable impurities, whereinbefore brazing heating, an amount of solid solution Si is 0.60 mass % orless, and an amount of solid solution Mn is 0.60 mass % or less, andwherein a recrystallization temperature in a temperature rise processduring the brazing heating is 450° C. or less.
 2. The aluminum alloy finmaterial for a heat exchanger according to claim 1, wherein in thealuminum alloy after brazing heating, an amount of solid solution Mn is0.60 mass % or less, and each of values of S1/S2 and Z1/Z2 is 1.20 orless when concentrations of Si and Zn in a vicinity of a grain boundaryare assumed to be S1 mass % and Z1 mass %, respectively, andconcentrations of Si and Zn in a matrix are assumed to be S2 mass % andZ2 mass %, respectively.
 3. The aluminum alloy fin material for a heatexchanger according to claim 1, wherein the aluminum alloy furthercomprises one or more selected from 0.05 to 0.30 mass % Cu, 0.05 to 0.30mass % Ti, 0.05 to 0.30 mass % Zr, 0.05 to 0.30 mass % Cr, and 0.05 to0.30 mass % V.
 4. A method of producing the aluminum alloy fin materialfor a heat exchanger according to claim 1, the method comprising a stepof casting the aluminum alloy, a hot-rolling step of hot-rolling a castingot, a cold-rolling step of cold-rolling a hot-rolled sheet, and oneor more annealing steps of annealing a cold-rolled sheet in or after thecold-rolling step, or in and after the cold-rolling step, wherein thehot-rolling step comprises a heating stage, a retention stage, and ahot-rolling stage, wherein in the heating stage, a heating rate fromattainment of 400° C. to attainment of a retention temperature in theretention stage is 60° C./h or less, wherein in the retention stage, theretention temperature is 450 to 560° C., and a retention time is 0.5hour or more, wherein in the hot-rolling stage, a time for which thehot-rolled sheet has a temperature of 400° C. or more is 5 minutes ormore, and wherein in the cold-rolling step, the cold-rolled sheet has atemperature of 120° C. or less.
 5. A method of producing the aluminumalloy fin material for a heat exchanger according to claim 1, the methodcomprising a step of casting the aluminum alloy, a homogenizationtreatment step of homogenization-treating a cast ingot, a hot-rollingstep of hot-rolling a homogenization-treated ingot, a cold-rolling stepof cold-rolling a hot-rolled sheet, and one or more annealing steps ofannealing a cold-rolled sheet in or after the cold-rolling step, or inand after the cold-rolling step, wherein the homogenization treatmentstep comprises a heating stage, a retention stage, and a cooling stage,wherein in the heating stage, a heating rate from attainment of 400° C.to attainment of a retention temperature in the retention stage is 60°C./h or less, wherein in the retention stage, the retention temperatureis 450 to 560° C., and a retention time is 1.0 hour or more, wherein inthe cooling stage, a cooling rate before the ingot attains a temperatureof 400° C. is 60° C./h or less, and wherein in the cold-rolling step,the cold-rolled sheet has a temperature of 120° C. or less.
 6. A heatexchanger to which the aluminum alloy fin material according to claim 1is assembled by brazing.
 7. A method of producing the heat exchangeraccording to claim 6, the method comprising subjecting a combination ofthe aluminum alloy fin material according to claim 1 with another memberto brazing heating at an attainment temperature of 590 to 615° C. for 2to 6 minutes, wherein a recrystallization temperature in a temperaturerise process during brazing is set at 450° C. or less, and a heatingrate in a temperature range of 300 to 580° C. is set at 60 to 160°C./min.